Electrophoretic dip painting installation

Abstract

The invention relates to an electrophoretic dipping system comprising at least one bowl (1) which can be filled with a liquid and an object which is to be coated and which can be dipped therein. At least one power supply unit (5A, 5B, 5C) produces DC voltage with definite residual ripple from AC voltage. The one pole thereof can be connected to at least one electrode of a first polarity (3A, 3B, 3C), said electrode being arranged in the dipping bowl (1) and the other pole thereof can be connected to the object which is to be coated. The power supply unit (5A, 5B, 5C) comprises one uncontrolled diode rectifler bridge (19) and an IGBT switch (22) which comprises a controllable oscillator (24) and a power transistor (23). The controllable oscillator (24) generates pulses having a repetition frequency ranging from between 5 and 30 kHz with variable pulse widths. The power transistor (23) is controlled by said pulses. The voltage pulses produced therefrom can be smoothed out with the aid of relatively small smoothing elements until a highly reduced residual ripple which benefits the quality, especially the smoothness and the roughness of the applied protective coating is obtained. Said power supply unit (5A, 5B, 5C) also has a highly improved cos Φ compared to currently known thyristor bridge switches used for the same purpose.

Dependencies are inferred from the claim text.